Digital cameras that employ fixed focal length lenses are used in mobile devices such as cell phones, laptops and other devices. Such cameras have a wide angle lens that results in a short and fixed focal length. Auto focus operations are known wherein a user of the cell phone or digital camera may hold down a push button halfway to auto focus an image whereafter the user may then continue to press the button to the fully pressed position to capture the final image. However, known auto focus operations may move the lens in a uniform manner such as every 25 positions throughout its range of, for example, 255 positions and capture an image at every uniform lens position of 25 positions resulting in the processing of 10-12 frames. Capturing 10 or so images from which the auto focus algorithm determines the best image can result in power drain for the mobile device and over time drastically impact battery usage. In addition, if the flash is used to take the final image, when a flash may not actually be necessary or useful, the additional power drain can degrade the performance of the mobile device. In addition, with the uniform focus lens position scheme, 10 or 12 frames may be taken which requires the device to capture and process many frames for the auto focus determination. This can require additional processing time and the user may have to wait an unnecessary amount of time for the auto focus operation to be completed.
It is also known to use nonuniform lens positions as part of an autofocus process. For example, to find the best lens position, various auto-focus searching strategies can be used. These methods determine how the lens position is updated (by how much and in which direction). The searching method can affect the speed and accuracy of auto-focus process. The set of lens positions used to find the best lens position could be based on non-uniform (or uniform) intervals. Non-uniform lens positions are typically established dynamically on the fly based on a determined rate of change of focus-metric values. That is, if the rate of change of focus-metric value is determined by a process in the device to be high, shorter lens position intervals are used while if the rate of change of focus-metric value is low, longer intervals are used. However, it can be difficult to determine the rates of change and then determine a suitable interval to use.
Improving auto focus speed and reducing power drain on mobile devices or non-mobile devices is extremely important, particularly as mobile device usage increases drastically. The need for such improvements have existed for many years. However, known current solutions still can require unnecessary amounts of time and/or power consumption.
As to depth map generation, multi-camera image processing systems (e.g., a calibrated stereo vision system) may employ multiple cameras each employing a lens to generate an image depth map that includes regions of interest of a field of view to be used for different applications such as in automated-vehicle guidance systems for guiding vehicles. Generating depth maps using such systems can result in a highly complex and expensive process requiring multiple pre-calibrated cameras. However, a need also exists for simpler depth-map generation (e.g., segmenting the field of view into foreground and background) to be used for improving various digital camera functions/operations such as a more effective use of flash/no-flash selection, better exposure estimation, more effective white balancing and improved color-correction-matrix selection.